I have reviewed the relevant Idaho laws.
I percieve two potential claims for you.
If someone wrongfully has your personal property, then the general remedy is a lawsuit called a "claim and delivery." You can find the relevant ID statutes for this process here: http://law.justia.com/idaho/codes/08ftoc/08003ktoc.html. I could not find a sample Complaint to use for this action online.
This link here has a sample of the Writ that is issued by the Court.
There are, however, a couple of problems with this process. First, you must post a bond to use this procedure. Second, it is not clear that this would apply to your phone system, which I am inferring has become to some extent incorporated with the building. E.g., the Sheriff could not easily just go in the building and walk out with those items. (Also: this remedy is ideal where the other person never had a claim to the property. Here, the situation is a little muddy because the other party was originally in lawful possession of the item, and there is now a dispute.)
The other remedy would be to file a lien. You are probably entitled to assert such a lien under ID law, if you are not beyond your deadlines. You can find a discussion of that law in ID here: http://lawdigest.uslegal.com/contractors/construction-liens/1652/.
The interplay between bankruptcy and this type of lien is very complicated, but you will probably have a fairly good position in any bankruptcy proceeding (i.e. ahead of most unsecured creditors).
I do not have a terrific answer for you here to avoid your risk, and there is a chance that you could take a partial or complete hit here. You probably do not have a right to simply reclaim your property. If the property is easily removed, then you could try a "claim and delivery," but that is somewhat problematic also.
As for your last question, I think it would be risky for your employee to walk out with the equipment. The other party has a sufficient interest in the property to render your employee in some jeopardy of violating a criminal law if he leaves with the items.
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